The present invention relates to a fuel injection controller, and more particularly, to a fuel injection controller for a cylinder injection engine that injects fuel directly into a combustion chamber.
Japanese Unexamined Patent Publication No. 10-30468 describes a controller for a cylinder injection engine, which injects fuel directly into a combustion chamber. The controller controls fuel injection in accordance with the operating state of the engine and selectively injects fuel in the intake stroke (intake stroke injection mode) and the compression stroke (compression stroke injection mode). In a typical cylinder injection engine, if compression stroke injection is performed when the temperature of the combustion chamber is low, the time provided for vaporizing the fuel is short. Thus, the fuel is not vaporized as desired. This affects combustion and increases the amount of unburned gases in the emissions. To prevent such emissions when the engine is started and the engine coolant temperature is relatively low, the time for vaporizing the injected fuel is lengthened by injecting fuel during the intake stroke. When the engine is started and the coolant temperature is relatively high, fuel is injected during the compression stroke. This improves fuel efficiency and the exhaust gas emissions. However, in the cylinder injection engine, due to the different fuel injection timing, the manner in which fuel deposits in the combustion chamber when the engine is cool differs between the intake stroke injection mode and the compression stroke injection mode.
However, in the conventional cylinder injection engine, intake stroke injection and compression stroke injection are controlled without taking into consideration the deposition of the fuel on the surfaces of the combustion chamber when the engine is cool. This hinders combustion thereby producing undesirable exhaust gas emissions and lower performance.
It is an object of the present invention to provide a if fuel injection controller for a cylinder injection engine having improved exhaust gas emissions and drivability when the engine is cool.
To achieve the above object, the present invention provides a fuel injection controller of a cylinder injection engine that selects an injection mode from various fuel injection modes including an intake stroke injection mode, in which fuel is injected during an intake stroke, and a compression stroke injection mode, in which fuel is injected during a compression stroke. The controller includes a selection means for selecting the compression stroke injection mode when the engine is cool if the temperature of the engine when the engine is started is within a predetermined temperature range and for selecting the intake stroke injection mode when the engine is cool if the temperature of the engine when the engine is started is higher than the predetermined temperature range.
A further aspect of the present invention provides a method for controlling fuel injection in a cylinder injection engine that selects an injection mode from various fuel injection modes including an intake stroke injection mode, in which fuel is injected during an intake stroke, and a compression stroke injection mode, in which fuel is injected during a compression stroke. The method includes selecting the compression stroke injection mode when the engine is cool if the temperature of the engine when the engine is started is within a predetermined temperature range, and selecting the intake stroke injection mode when the engine is cool if the temperature of the engine when the engine is started is higher than the predetermined temperature range.